Name Period __ Date _

:Introduction

Environmental conditions act as selecting agents because they select organisms with the most beneficial

traits to become the parents of the next generation. Within a species, individuals with variations that

make them better adapted to their environment will survive and reproduce in greater numbers than

those without such adaptations. Observations have shown that the offspring of better-adap~individuals

inherit many of their parents' favorable variations.

Finches are small birds found in many locations throughout the world. Charles Darwin used the

numerous finch species found on the Galapagos Islands as evidence of natural selection. The great

variety of beak adaptations present on the Galapagos is thought to be due to the isolation of bird

populations on the islands with different kinds and amounts of food. Seed-eating finches exhibit a great

number of differences in beak shapes and sizes. During ongoing competition for resources. some finches

are successful and become more numerous, while less successful finches decrease in number.

In this labOratory activity, you will work with different tools that will serve to model finch "beaks."

The seeds provided represent finch food on a particular island. You will compete with other '1inch"

species to see which "beak" is best adapted for obtaining a specific food.

Objectives

In this laboratory activity, you will; • learn how structural differences may affect the survival rate of members within a species • simulate competition for resources among different species of organisms • see the role of the environment as a selecting agent

Safety

• You should wear safety goggles for this activity. • Handle the tools carefully. They may have sharp edges and could cause cuts.

• Be especially careful when two or more of you are reaching for seeds at the same time. The "beak" being used by one student has the potential to strike another student.

• Do not taste or eat any of the seeds.

Important Note: Record all ofyour data and answers on these laboratory sheets. You will need to keep them for review before the Regents Examination. Later, you will need to transfer your answers to a separate Student Answer Packet. Your teacher will use it in grading your work, and the school will retain it as evidem:e ofyour completion of the laboratory requirement for the Living Environment Regents Examination.

Materials for lEach Team

• 1 small plastic dish or cup • large seeds (such as lima beans)*

• 1 large nonbreakable dish • small seeds (such its lentils)

• 1 tool to serve as a ''beak'' • 2 pairs safety goggles

* may be needed depending on results of Round One

Procedures

1. Examine the different tools ("beaks") and seeds provided. Predict which "beak" will be the

most successful at picking up small seeds. Give the reasons for your choice.

2. Predict which ''beak'' will be the least successful at picking up small seeds. Give the reasons for

your choice.

3. - From this point on, you and your partner will model a finch feeding. The tool you were assigned

will be your "bealc" Describe what characteristics it has that make it good for picking up small

seeds. In the remaining space or on a separate sheet of paper, draw an outline of your assigned

"beak."

4. Both you and your p3l1ner should pmctice transfening the small seeds quickly from the large

dish to the small dish before the competition begins. The large dish of small seeds represents

the island environment where you live and feed. The small dish represents a finch stomach. You

may move only one seed at a time. You will receive credit only for a seed that falls into and

stays in ~e small dish.

Round On6: No Competitiony Original Island

5. When given the "Round One" signal, one member of your team should use the ~'beak" to pick up

small seeds one at a time from the large dish and place them in the small dish. Repeat this for a

total of four trials, two trials for each partner. A timekeeper will tell you when to start and stop

each trial. Record your results in the "Round One: Feeding with No Competition" data table.

Round One: Feeding with No Competition

Seeds Collected

Partner #1 Trial #1

Trial #2

Partner #2 Trial #3

Trial #4

Average

6. Calculate the average number of seeds obtained during the four trials. Round off to the nearest seed. In order to "survive:' your species needs to collect an average of 13 seeds per trial. If you achieve that goal, you remain healthy and continue to live on the original island and eat small seeds.

Ifyour team averaged fewer than 13 small seeds per trial, you and your partner will "migrate" to a new island with a different food supply to avoid starvation. Ask your teacher to give you a new large dish that contains approximately 200 or more large seeds. This will be your island for Round Two. Perhaps your "beak" will be better adapted for feeding success in a new environment

Round Two: Competition In this round, instead. of feeding alone, you will be competing for food with finches that have different kinds of "beaks:' 'fo simulate this competition, your team will feed from the same disb as one other team. If you were successful during Round One, you will be feeding with other finches on .small seeds. If you were not successful. you will be competing for large seeds.

7. In the "Round Two: Feeding with Competition" data table, check the box that indicates whether you are feeding on the original island (small seeds) or on the new island (large seeds). Complete four trials just as you did the first time and record the results of each trial. Again, wait for the time keeper to tell you when to stan feeding and when to stop for each trial.

Round Two: Feeding with Competition

CJ Or'iginal island (small seeds) CI New island (large seedS)

Seeds Collected

Partner #1 I Trial #1

Trial #2

Partner #2 Trial #3

Tria)) #4

Average

-------------------------

8. Calculate the averag.e number of seeds obtained during the four trials. Round off to the nearest seed. If your team collected an average of 13 seeds or more per trial, you can go on to RQund

Three. If your team collected fewer than 13 seeds per trial, you and your partner are DOW

eliminated.

Round Three: Increased Competition

During this round, you will be competing with all of the other finch species left alive on your island.

In other words, all of the fmch teams that were successful at feeding on small seeds will compete at one dish containing small seeds. At the same time, all of the finches successful at feeding on large

seeds during Round Two will compete at one dish of large seeds.

9. In the "Round Three: Feeding with Increased Competition" data table, indicate whether you are

f~eding on small or large seeds. Complete four trials as before and record the results of each trial

and your average.

Round Three: Feeding with Increased Competition

o Original island (small seeds) a New island (large seeds)

Seeds Collected

Partner #1 Trial #1

Trial #2

Partner #2 Trial #3

Trial #4

Average

Analysis Questions

1. What characteristics of your "beak:" interfered with feeding success on the original island?

. 2. Name three traits other than beak characteristics that could contribute to the ability of a finch to

compete successfully.

3. It is very unlikely that.all of the beaks within a species of finch are exactly alike. Random mutations

and new gene combinations resulting from sexual reproduction are the source of beak variations.

Describe at least three beak. variations that could randomly appear and further improve your

species' chances of survival when feeding on small seeds.

4. Why did some ''beak'' types survive on the new island (with large seeds) when they could not

smvive on the original island?

5. ciass Activity: Complete the Class Results data table on the last page of this laboratory activity

before going on to the remaining questions.

6. Did those who were successful in Round One survive equally well when others were competing

for food at the same dish during Round Two? Support your answer with an explanation.

7. Why were there fewer survivors at the end of Round Three?

8. At the end of Round Three, were the types of "beaks" that were successful on the new island

the same as the types of beaks that were successful on the original island? Support

your answer with an explanation.

9. Explain how this activity simulates each of the concepts listed below as they are involved in the

process of natural selection. Describe a specific example from this laboratory for each concept.

variation: _

competition: _

struggle for survival: _

adaptation:

environment: , _

selecting agent: _

Base your answers to questions 10-12 on Figur-e 1. which shows various finches found on the Galapagos Islands, and on your knowledge of biology.

Sharp-billed Ground Finch

Large free Finch

-Small Tree Finch

- from Galapagos: A Natural History Guide

Figure 1. Variations in Beaks of Galapagos Islands Finches

10. Predict which species of finch would be most likely to survive if the weather on the Galapagos

Islands gradually changed and the seeds available to the finches became larger with heavier

coverings. Support your answer with an explanation.

1i. One island is populated by two species-Ground Finches and Small Tree Finches.

a. What two types of food would you expect to be available on this island? Support your

answer.with an explanation.

b. Would you expect the two species to compete for food on this island? Support your answer

with an explanation.

c. How might the two native finch populations be affected if several dozen Sharp-billed

Ground Finches were to migrate to the island and survive? Support your answer with an

explanation.

12. a. Explain how an island could support large populations of both Large Ground Finches and

Small Ground Finches.

b. How could you use the materials provided in this lab to test your explanationl

Data Table for Question #5 of the Analysis Questions

Class Results

Beaks That Were NumberoC Characteristics of Beaks Beak Types (Size and Shape)

Present at the beginning of the activity

I

Successful at feeding in Round One on the original island-fed on small seeds, did not need to migrate

I

Not successful at feeding in Round One on the original island-fed on small seeds. had to migrate to the new island

Successful at feeding in Round Two Ion the original island-fed on small seeds

-Successful at feeding in Round Two on the new island-fed on large seeds

. Not successful at feeding in Round Two on either island-species dies out

Successful at feeding in Round Three on the original island-fed on small seeds

,

Successful at feeding in Round Three I on the new island-fed on large seeds

Not successful at feeding in Round Three on either island-species eliminated